These are the most (and least) crowded Wall Street trades right now

Todd Evans, animal handler with Dawn Animal Agency, holds the Aflac Duck on the floor of the New York Stock Exchange in New York.

A critical metric fund managers often look at is how "crowded" a stock is in term of institutional ownership (hedge funds and mutual funds) and then take the other side.

So-called "crowded" trades are those with many similarly-minded participants who can overextend the price of an asset; wary investors can then bet against this crowd movement and capitalize when the crowd frenzy ends.

UBS compiled a list of the "top 10 crowded trades" for clients, in which the firm's analysts highlight the stocks most overweight by global active fund managers.

The firm also created a list of the least crowded trades, which contrarian investors may seek out to find hidden value.

UBS' Shanle Wu's team collected all the positions from global active fund managers using FactSet institutional ownership data. The team then compared the weightings versus the "relative equity index benchmark" to calculate the investor and active net weight percentages.